Use _expr in array definitions

[benber86]

What I did

Modified the lark grammar to support expressions when specifying array length on definition.
For instance trying to parse the following valid Vyper code with lark:

a: public((uint256[4 & 4]))

or

B: constant(uint256) = 2
c: DynArray[uint256, B**2]

@external
def __init__(
    initial_prices: uint256[3+B-2%1]
):
    pass

Will currently raise an UnexpectedToken exception

How I did it

Replaced (DEC_NUMBER | NAME) with _expr in grammar.lark for array_def and dyn_array_def

How to verify it

Parsing the following code:

a: public((uint256[4 & 4]))
B: constant(uint256) = 2
c: DynArray[uint256, B**2]

@external
def __init__(
    initial_prices: uint256[3+B-2%1]
):
    pass

Properly returns the following tree:

Tree(Token('RULE', 'module'), [Tree(Token('RULE', 'variable_def'), [Tree(Token('RULE', 'variable_with_getter'), [Token('NAME', 'a'), Tree(Token('RULE', 'type'), [Tree(Token('RULE', 'tuple_def'), [Tree(Token('RULE', 'array_def'), [Token('NAME', 'uint256'), Tree('bitand', [Token('DEC_NUMBER', '4'), Token('DEC_NUMBER', '4')])])])])])]), Tree(Token('RULE', 'constant_def'), [Tree(Token('RULE', 'constant_private'), [Token('NAME', 'B'), Tree(Token('RULE', 'constant'), [Tree(Token('RULE', 'type'), [Token('NAME', 'uint256')])])]), Token('DEC_NUMBER', '2')]), Tree(Token('RULE', 'variable_def'), [Tree(Token('RULE', 'variable'), [Token('NAME', 'c'), Tree(Token('RULE', 'type'), [Tree(Token('RULE', 'dyn_array_def'), [Token('NAME', 'uint256'), Tree('pow', [Tree('get_var', [Token('NAME', 'B')]), Token('DEC_NUMBER', '2')])])])])]), Tree(Token('RULE', 'function_def'), [Tree(Token('RULE', 'decorators'), [Tree(Token('RULE', 'decorator'), [Token('NAME', 'external')])]), Tree(Token('RULE', 'function_sig'), [Token('NAME', '__init__'), Tree(Token('RULE', 'parameters'), [Tree(Token('RULE', 'parameter'), [Token('NAME', 'initial_prices'), Tree(Token('RULE', 'type'), [Tree(Token('RULE', 'array_def'), [Token('NAME', 'uint256'), Tree('sub', [Tree('add', [Token('DEC_NUMBER', '3'), Tree('get_var', [Token('NAME', 'B')])]), Tree('mod', [Token('DEC_NUMBER', '2'), Token('DEC_NUMBER', '1')])])])])])])]), Tree(Token('RULE', 'body'), [Tree(Token('RULE', 'pass_stmt'), [])])])])

Commit message

Use _expr in array definitions in lark grammar

Description for the changelog

Cute Animal Picture

[codecov-commenter]

Codecov Report

Merging #3131 (ea5c453) into master (676dc30) will decrease coverage by 0.58%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3131      +/-   ##
==========================================
- Coverage   88.49%   87.91%   -0.59%     
==========================================
  Files          95       95              
  Lines       10760    10756       -4     
  Branches     2266     2201      -65     
==========================================
- Hits         9522     9456      -66     
- Misses        796      856      +60     
- Partials      442      444       +2     

Impacted Files	Coverage Δ
vyper/codegen/arithmetic.py	70.96% <0.00%> (-13.65%)	⬇️
vyper/semantics/types/value/numeric.py	80.45% <0.00%> (-4.60%)	⬇️
vyper/ir/s_expressions.py	91.17% <0.00%> (-2.95%)	⬇️
vyper/builtin_functions/functions.py	87.84% <0.00%> (-2.70%)	⬇️
vyper/ast/nodes.py	92.72% <0.00%> (-0.50%)	⬇️
vyper/codegen/abi_encoder.py	88.46% <0.00%> (-0.11%)	⬇️
vyper/semantics/validation/module.py	85.41% <0.00%> (-0.08%)	⬇️
vyper/codegen/core.py	85.15% <0.00%> (-0.03%)	⬇️

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